// SPDX-License-Identifier: GPL-2.0
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/*
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* Tests for prctl(PR_GET_TSC, ...) / prctl(PR_SET_TSC, ...)
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*
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* Tests if the control register is updated correctly
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* when set with prctl()
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*
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* Warning: this test will cause a very high load for a few seconds
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*
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <signal.h>
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#include <inttypes.h>
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#include <wait.h>
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#include <sys/prctl.h>
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#include <linux/prctl.h>
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/* Get/set the process' ability to use the timestamp counter instruction */
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#ifndef PR_GET_TSC
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#define PR_GET_TSC 25
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#define PR_SET_TSC 26
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# define PR_TSC_ENABLE 1 /* allow the use of the timestamp counter */
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# define PR_TSC_SIGSEGV 2 /* throw a SIGSEGV instead of reading the TSC */
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#endif
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/* snippet from wikipedia :-) */
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static uint64_t rdtsc(void)
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{
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uint32_t lo, hi;
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/* We cannot use "=A", since this would use %rax on x86_64 */
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__asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
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return (uint64_t)hi << 32 | lo;
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}
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int should_segv = 0;
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static void sigsegv_cb(int sig)
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{
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if (!should_segv)
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{
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fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled\n");
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exit(0);
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}
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if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0)
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{
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perror("prctl");
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exit(0);
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}
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should_segv = 0;
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rdtsc();
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}
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static void task(void)
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{
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signal(SIGSEGV, sigsegv_cb);
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alarm(10);
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for(;;)
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{
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rdtsc();
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if (should_segv)
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{
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fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled\n");
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exit(0);
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}
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if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0)
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{
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perror("prctl");
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exit(0);
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}
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should_segv = 1;
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}
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}
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int main(void)
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{
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int n_tasks = 100, i;
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fprintf(stderr, "[No further output means we're allright]\n");
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for (i=0; i<n_tasks; i++)
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if (fork() == 0)
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task();
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for (i=0; i<n_tasks; i++)
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wait(NULL);
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exit(0);
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}
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